1. Field of the Invention
The present invention relates to a shutter device for use in a camera, an image display device and other devices.
2. Related Background Art
Many kinds of cameras and the like employ a focal plane shutter in which a blade group, which is divided to plural pieces by a parallel link mechanism constituted of two arms, is supported freely rotatably. As for the type of the parallel link mechanism used for such a focal plane shutter, according to a long-arm type, an arm proximal end is mounted freely rotatably on one portion of both side portions of a shutter opening in a shutter base plate, while a portion on the arm front end side is joined to the other side of the blade group (the arm being disposed such that it strides over from one side of the shutter opening to the other side), and according to a short-arm type, an arm proximal end is mounted freely rotatably on one portion of both side portions of the shutter opening in the shutter base plate while a portion on the arm front end side is joined to the one side of the blade group (the arm being disposed such that it does not stride over from one side of the shutter opening to the other side).
As the focal plane shutter, a so-called vertically-traveling type focal plane shutter in which the blade group travels vertically has been often used.
In the long-arm type of the vertically-traveling type focal plane shutter, as disclosed in Japanese Utility Model Publication No. 35-29651, the blade group is held freely rotatably on an opposite side to the arm proximal end across the shutter opening. For the reason, the arms are formed longer than the width of the shutter opening.
Because, in the long-arm type, a rotation angle of the arm necessary for opening/closing the shutter opening by means of the blade group may be small, a deflection amount in a direction (lateral direction) perpendicular to the traveling direction of the blade group upon opening/closing operation is small, which is advantageous for reduction of the lateral width of the shutter. If the number of the blades held by two arms is three or more, the structure becomes complicated and long arms need to be used. Thus, inertia of a blade unit comprised of the blade group and arms increases, which is disadvantageous for high-speed operation of the shutter.
For the reason, with increased speed in exposure second-basis time of a shutter and increased speed in flash light emission synchronous second-basis time in recent years, the long-arm type not suitable for high-speed operation has been refrained from use.
On the other hand, although the short-arm type is disadvantageous for reduction of the lateral width as compared to the long-arm type, its arms do not stride over the shutter opening and a plurality of blades are supported freely rotatably with two arms on a side near the arm proximal end. Further, to decrease inertia by the traveling of the blades, it is preferable that the arm length is as short as possible.
The structure and dimensions of respective components of the short-arm type focal plane shutter are shown in FIGS. 22 to 24 (FIG. 22 shows a traveling preparation completion state, FIG. 23 shows a traveling completion state, and FIG. 24 shows a state of blade movable end (over-charge max)).
In this shutter device, proximal ends of a first front curtain arm 106 and a second front curtain arm 107 are mounted freely rotatably around shafts 101d, 101e on a shutter base plate 101 having a shutter opening 101a. A slit forming blade 102 and four covering blades 103, 104, 105, 105xe2x80x2, which constitute the front curtain having five-blade structure are mounted freely rotatably on the two front curtain arms 106, 107 through caulking dowels 108a to 108e and 109a to 109e so as to form parallel links.
Further, proximal ends of a first rear curtain arm 114 and a second rear curtain arm 115 are mounted freely rotatably around shafts 101f, 101g on the shutter base plate 101. Then, a slit forming blade 110 and three covering blades 111, 112, 113, which constitute the rear curtain having four-blade structure, are mounted freely rotatably on the two rear curtain arms 114, 115 through caulking dowels 116a to 116d and 117a to 117d so as to form parallel links.
On the front curtain side and the rear curtain side, the blade caulking dowels are arranged such that they draw a smooth curve. The first arm and the second arm are disposed adjacent each other in a state in which the front curtain and the rear curtain overlap (hereinafter, this shutter device is called a first conventional example).
In addition, Japanese Utility Model Publication No. 6-26896 has disclosed a shutter device which adopts a third (further, a fourth) auxiliary arm to achieve miniaturization for a reason that the miniaturization is impossible with the parallel link composed of two arms. In this shutter device, when blades are overlapped, first and second arm supporting portions for supporting the slit forming blades are accommodated in an accommodating region existing between a finder and an opening window and the third arm for supporting other covering blades is located out of the region, thereby reducing the external shape dimensions in the horizontal direction of the shutter device.
Because in this shutter device, three arms are disposed in a small space, each arm is formed narrow and the rotation center of the proximal end of the third arm exists between the proximal end rotation center of the first arm and the caulking dowel of the third covering blade when blades are overlapped, while the caulking dowel of the third covering blade on the first arm exists between the proximal end rotation center of the third arm and the caulking dowel of the third covering blade (hereinafter, this shutter device is called a second conventional example).
Moreover, a shutter device (hereinafter this is called a third conventional example) disclosed by Japanese Utility Model No. 2501747 is provided with a slit forming blade driven by a first parallel link mechanism and covering blades driven by a second parallel link mechanism. A joining distance of the first parallel link on the slit forming blade is made longer than the joining distance of the second parallel link on the covering blade so as to maintain parallelism of the slit forming blades and reduce space from the shutter opening to the proximal end side of each parallel link.
On the other hand, Japanese Utility Model Publication No. 59-28414 has disclosed a focal plane shutter in which at least the slit forming blades in opening/closing blade groups divided to plural pieces are driven vertically by a parallel crank mechanism below a finder disposed on the top of a camera main body. Of both blade groups in this device, the degree of dividing of a blade group folded upward is made higher than the degree of dividing of a lower blade group, and of the upper blade group, at least pairing components constituting the parallel crank mechanism on the slit forming blade are located out of a region restricted in a vertical direction of the finder portion. Further, a top portion of the pairing portion is located above the lower edge of the finder portion so as to prolong the length of a section in the vertical direction. Consequently, a slit width upon exposure operation is stabilized and the top end of the shutter located at the top of the shutter opening is brought near the shutter opening without affecting exposure badly so as to set the finder position near the opening, thereby reducing the camera size (hereinafter this is called a fourth conventional example).
Generally, if the reduction in shutter size, particularly the lateral width, is achieved, the number of joint sections between the arm and the blade decreases as the number of divided blades decreases. Thus, area occupied by the joint sections decreases, which is advantageous for reduction of the lateral size.
In contrast, if the number of the blades is decreased, the overlapping amount of blades for shielding the shutter opening of a predetermined size decreases, thereby making it difficult to secure light shielding performance. In addition, because the width of each blade cannot be made so smaller, this measure is disadvantageous for reducing the size in a height direction by bringing a shutter top end located at the top of the shutter opening to near the shutter opening.
If the arm length is shortened to aim at the reduction of the size according to the first conventional example, freedom of supporting positions for supporting the covering blades freely rotatably drops because the front curtain is comprised of five blades and the blade caulking dowels are arranged just in line with each small interval. Thus, an interference occurs in the blade unit (for example, an interference between the outer periphery of a proximal end 106b of the first arm 106 and outer peripheries of the second arm 107 and covering blade 105xe2x80x2 around the blade caulking dowel 109e, an interference between the outer periphery of the first arm 106 around the blade caulking dowel 108e and the outer peripheries of the second arm 107 and covering blades 104, 105 around the blade caulking dowels 109c, 109d and the like). Therefore, a rotation operating angle of the arm cannot be increased (because the size of the shutter opening in the blade traveling direction is specified, if the arm length in the parallel link is decreased, it is necessary to increase the arm rotation operating angle to move the blade by a specified distance). Further, there exists such an inconvenience that the overlapping amount between the slit forming blade and the covering blade is difficult to maintain when the blades are expanded to close the shutter opening, which blocks an effective reduction of the size.
On the other hand, when the rear curtain having the four-blade structure is used commonly for the front curtain, the overlapping amount of blades is as small as about 2 mm when the rear curtain is expanded. Even if the respective blades are expanded within a range permitted by the blade storage space in the overlapping state in which the front curtain opens the shutter opening, the freedom of supporting positions which support the covering blades freely rotatably is decreased by restriction on the arrangement of the blade caulking dowels, because the blade caulking dowels are arranged just in line with a small interval like the above-described blade having five-blade structure. Consequently, an interference occurs in the blade unit (for example, an interference between the outer periphery of the proximal end 114b of the first arm 114 and outer peripheries of the second arm 115 and covering blades 113 around the caulking dowel 117d, an interference between the outer periphery of the first arm 114 around the blade caulking dowel 116d and the outer peripheries of the second arm 115 and covering blade 112 around the blade caulking dowel 117c and the like). Therefore, the blade traveling distance can be expanded only by about 1 mm in the blade traveling direction and in its opposite direction. As a result, the desired overlapping amount of 4 mm cannot be secured and further, no remarkable reduction of the size is achieved. As regards a description about the arrangement of the caulking dowels, see (6) described later.
Further, in the first conventional example, the rear curtain which is overlapped on the top portion of the shutter, affecting the lower edge position of the finder portion of a single lens reflex camera will be described below.
When the first arm 114 is located at its movable end in the rear curtain overlapping state, an angle formed between a line L connecting the rotation center of the proximal end of the first arm 114 and the rotation center of a front end caulking dowel 116a of the same arm and a direction parallel to the shutter opening face and perpendicular to the blade group traveling direction (for example, line X) is assumed to be xcex1. At this time, xcex1 is 41.5xc2x0.
When a dimension from the rotation center of the proximal end of the first and second arms constituting a parallel link to the rotation center of a caulking dowel supporting the slit forming blade at the arm front end is assumed to be D, because the D is 23 mm, a traveling distance xcex94y of the slit forming blade 111 per unit angle in the traveling direction from a state in which the first arm 114 is located at the operable end when the rear curtain is overlapped is 0.3 mm/deg.
Unless no adjustment or the like is made in the focal plane shutter, the start position held before exposure of the blades or the over-charge position may be deflected by about 1xc2x0 in terms of the arm rotation angle due to disparity of component accuracy or assembly error.
Therefore, although the rear curtain is held at the start position with an angle 38.5xc2x0, which is in the vicinity of this angle xcex1=41.5xc2x0, because the xcex94y is as relatively large as 0.32 mm/deg, deflection in the position (angle) held by a control magnet (not shown) affects deflection in the start position of the rear curtain slit forming blade 111 largely. For the reason, there is such an inconvenience that it is difficult to hold the second-basis time accuracy in an excellent condition because the deflection in the start position of the rear curtain slit forming blade 111 affects the shutter second-basis time accuracy directly.
Likewise, because the traveling distance of the slit forming blade 111 per unit angle at the rear curtain maximum charging angle (over-charge max), which coincides with the aforementioned xcex1, is substantially equal to xcex94y=0.3 mm/deg, which is still relatively large, the lower edge position of the finder portion has to be determined by providing with an allowance considering this deflection. Therefore, there is such an inconvenience that the height of the camera is raised by the amount corresponding to this allowance.
Because according to the second conventional example, the third arm for supporting the covering blade group is attached, the structure is more complicated as compared to a general parallel link mechanism constituted of two arms like the first conventional example and operating resistance is increased, so that inertia of the blade unit is also increased.
Also, because three arms are disposed in a small space, each arm is formed narrow, so that the strength of the arm itself drops. Further, because when the blades are overlapped, supporting portions of the first and second arms for supporting the slit forming blade are accommodated in an accommodating region existing between the finder and the opening window, the joining distance on the slit forming blade of the parallel link is decreased, so that the parallelism of an exposure slit is difficult to maintain.
Because, as for numerical values corresponding to the first conventional example, it comes that xcex1=30xc2x0, D=24 mm, xcex94y=0.36 mm/deg, deflection in the start position of the rear curtain slit forming blade is so large that the second-basis time is difficult to maintain excellently. Further, because deflection of the rear curtain maximum charging angle (over-charge max) is large, the lower edge position of the finder portion has to be determined by providing with an allowance considering this, so that the height of the camera is increased by just the amount corresponding to this allowance.
Further, according to the third conventional example, a single blade unit is provided with two parallel link mechanism and the third arm (further, a fourth arm) for supporting the covering blade group is added. Therefore, its structure becomes more complicated as compared to a general parallel link mechanism constituted of two arms like the first conventional example and additionally, operating resistance is increased, so that inertia of the blade unit is also increased.
Also, because three (or four) arms are disposed in a space reduced for miniaturization, each arm is formed narrower, so that the strength of the arm itself drops.
Further, a numerical value corresponding to the above described first conventional example is xcex1=40xc2x0 and if D=23 mm is assumed like the first conventional example, it comes that xcex94y=0.31 mm/deg. Therefore, deflection in the start position of the rear curtain slit forming blade is large, so that the second-basis time accuracy is difficult to maintain excellently. In addition, because deflection in the rear curtain maximum charging angle (over-charge max) is large also, the lower edge position of the finder portion has to be determined by providing with an allowance considering this deflection, so that the height of the camera is increased just by the amount corresponding to this allowance.
The fourth conventional example does not state anything about reduction in size of the lateral width of the shutter and intends to reduce the size of a camera by bringing the shutter top end located at the top position of the shutter opening near the shutter opening so as to bring the finder position near the opening, thereby achieving reduction of the camera. According to FIG. 3 indicating the fourth conventional example, a numerical value corresponding to the first conventional example is xcex1=34xc2x0 and if D=23 mm is assumed like the first conventional example, it comes that xcex94y=0.33 mm/deg. Therefore, deflection in the start position of the rear curtain slit forming blade is large, so that the second-basis time accuracy is difficult to maintain excellently. Further, because deflection in the rear curtain maximum charging angle (over-charge max) is large also, the lower edge position of the finder portion has to be determined by providing with an allowance considering this deflection, so that the height of the camera is increased just by the amount corresponding to this allowance.
Therefore, the second and third conventional examples are disadvantageous for high-speed traveling of the blade unit and for example, in case of a camera, a shorter exposure second-basis time than {fraction (1/4000)} seconds or a shorter strobe synchronous second-basis time than {fraction (1/200)} seconds is difficult to achieve. Further, because a shutter charging energy necessary for realizing the same curtain speed is increased, enlargement in size of the camera is induced or inconvenience occurs when the frame speed is increased for continuous photographing.
Also, according to the conventional examples, because the angle xcex1 is relatively small, deflection in the start position of the rear curtain slit forming blade is so large that it is difficult to maintain the second-basis time accuracy excellently. Additionally, because deflection in the rear curtain maximum charging angle (over-charge max) is large, the lower edge position of the finder portion has to be determined by providing with an allowance considering this, so that the height of the camera is raised just by the amount corresponding to this allowance.
Accordingly, an object of the present invention is to provide a short-arm type shutter device having a structure suitable for high-speed operation and securing an excellent operating efficiency, in which the size thereof in a direction (lateral direction) perpendicular to a blade traveling direction is reduced and the size thereof up to a shutter top end located at the top portion of a shutter opening is also reduced, while a sufficient blade overlapping amount for light shielding is secured and inertia of the blade unit is decreased.
To achieve the above-described object, according to an aspect of the present invention, there is provided a shutter device comprising: a shutter base plate having a shutter opening; a first arm member which rotates with a first shaft as a rotation center relative to the shutter base plate; a second arm member which rotates with a second shaft as a rotation center relative to the shutter base plate; and plural shutter blades, wherein each of the plural shutter blades is joined to the first and second members and when the first and second arm members rotate with respect to each shaft, the plural shutter blades travel over the shutter opening in a predetermined direction, and in a state in which the plural shutter blades are positioned in their overlapping state, when an angle formed between a line connecting the rotation center of the first arm with a connecting center to the first arm member of a shutter blade, located on a front end side (opposite side to the first rotation center) of the first arm member and a direction perpendicular to the predetermined direction is assumed to be xcex1, a condition of 45xc2x0xe2x89xa6xcex1xe2x89xa650xc2x0 is satisfied.
Preferably, when a dimension (length) from the rotation center of the first arm member to the connecting center of the shutter blade located on the front end side of the first arm member is assumed to be D and a dimension (length) of an opening of the shutter opening in the predetermined direction is assumed to be A, a condition of 0.78Axe2x89xa6Dxe2x89xa60.90A is satisfied.
Further according to another aspect of the present invention, there is provided a shutter device comprising: a shutter base plate having a shutter opening; a first arm member which rotates with a first shaft as a rotation center relative to said shutter base plate; a second arm member which rotates with a second shaft as a rotation center relative to said shutter base plate; and plural shutter blades, wherein each of the plural shutter blades is joined to said first and second members and when said first and second arm members rotate with respect to each shaft, said plural shutter blades travel over said shutter opening in a predetermined direction, and when a distance from a connecting center to the said first arm member of a shutter blade located at a front end side (opposite side to said first rotation center) of the first arm member to an end portion of the shutter blade near said connecting portion is assumed to be H and the width of the shutter blade in said predetermined direction is assumed to be W, a condition of 0.3Wxe2x89xa6Hxe2x89xa60.4W is satisfied.
According to still another aspect of the present invention, there is provided a shutter device comprising: a shutter base plate having a shutter opening; a first arm member which rotates with a first shaft as a rotation center relative to said shutter base plate; a second arm member which rotates with a second shaft as a rotation center relative to said shutter base plate; and plural shutter blades, wherein each of the plural shutter blades is joined to said first and second arm members and when said first and second arm members rotate with respect to each shaft, said plural shutter blades travel over said shutter opening in a predetermined direction, and when a distance from a connecting center to said first arm member of a shutter blade located adjacent a shutter blade joined to the front end side (opposite side to said first rotation center) of the first arm member to an end portion of the adjacent shutter blade near the connecting center is assumed to be H2 and the width of the adjacent shutter blade in said predetermined direction is assumed to be W2, a condition of 0.26W2xe2x89xa6H2xe2x89xa60.34W2 is satisfied.
According to a further aspect of the present invention, a shutter device comprising: a shutter base plate having a shutter opening; a first arm member which rotates with a first shaft as a rotation center relative to said shutter base plate; a second arm member which rotates with a second shaft as a rotation center relative to said shutter base plate; and four shutter blades, wherein each of the four shutter blades is joined to said first and second arm members and when said first and second arm members rotate with respect to each shaft, each of said shutter blades travels over said shutter opening in a predetermined direction, and of respective connecting portions in said first arm member, a brim portion protruded from an arm face at the connecting portion located at a second shortest distance from said rotation center of said first arm does not invade into said opening during an operation of opening/closing said opening of said shutter blade.
Preferably, the brim portion is disposed nearer the base plate than the face of the first arm.
The above-described features will be made apparent from following drawings and a description thereof.